For an industry that hinges on sensing the zeitgeist, the world’s biggest ad agencies aren’t handling a slow-burning controversy over their U.S. billing practices with much finesse. Ad firms such as WPP and Omnicom need to win back the trust of big brands like Coca-Cola, Ford and Unilever quickly or risk eroding their most profitable business, namely placing ads for clients on TV, radio or online.

The Association of National Advertisers, representing almost 1,000 companies, on Tuesday released the results of an eight-month investigation that purports to show how agencies put their interests before their clients’ through techniques it called “pervasive” and “non-transparent”.

Read the full Bloomberg article here.